In the optoelectronics art, it has become increasingly popular to mount a plurality of optical components on a silicon substrate, a technology also known as silicon optical bench (SiOB) technology. (See, e.g., U.S. Provisional Application of Anigbo, Ser. No. 60/009116, filed Dec. 22, 1995.) Such assemblies typically include a semiconductor laser mounted on the surface of the silicon substrate in alignment with a lightguiding element such as a spherical lens which is mounted within a cavity formed in the silicon substrate. The lens is typically made of a high index material such as spinel or garnet, and is bonded to the cavity walls by means of an aluminum layer deposited on the substrate. (See U.S. Pat. No. 5,178,319 issued to Coucoulas which is incorporated by reference herein.)
While standard practice in planar silicon technology usually provides adequate aluminum adhesion, we have found that for some SiOB applications the aluminum layer can delaminate from the cavity surfaces during sawing of the substrate and/or during bonding of the lens because of inadequate adhesion. This problem is due at least in part to the difficulty in cleaning the cavity prior to bonding.
Therefore it is desirable to provide enhanced adhesion of the aluminum layer and more reliable bonding of the components to the substrate.